Ca modulates cell structure and division
During plant growth and development, cell structure remodeling and cell division are the primary processes, which involve the regulation of a series of cell wall and cytoskeleton related events.62,63Our study showed exogenous Ca supply influenced the expression of some cell wall and cytoskeleton related proteins (Table1). Alpha-1,4-glucan-protein synthase 1 (spot 68) have a role in the cell wall polysaccharides biosynthesis process.64 Xylose isomerase (spot 69) participates in the synthesis of xylose, which is an important structure component of cell wall.65 Cinnamyl alcohol dehydrogenase (spot 8) is the enzyme catalyzing the last step of lignin biosynthesis and is of vital importance to cell wall formation.66 In the present study, the abundance of pinoresinol-lariciresinol reductase (PLR, spot 7), a member of the pinoresinol-lariciresinol/isoflavone/phenylcoumaran benzylic ether reductase (PIP) family, that catalyzes two early steps in lignan biosynthesis67, was found to be increased under high Ca treatment (Table 1). Together, The up-regulation of the above four proteins under high Ca treatment suggest sufficient exogenous Ca potentially accelerate the biosynthesis and accumulation of substrates for cell wall assembly, and further facilitate P. massoniana seedling growth and development.
In plants, the actin cytoskeleton system is of vital significance to cell development and morphogenesis.68 The down-regulated actin 2 at low Ca level implying Ca deficiency suppressed the expression of actin 2, and resulted in distributed P. massoniana cell division and development. Under medium or high Ca level, increased expression of actin 2 was observed compared with low Ca level, suggesting cell actin cytoskeleton system is likely recovered.
Collectively, enough exogenous Ca supply is indispensible for P. massoniana cell structure reshaping and cell division in the process of plant growth and development.